This invention relates to improved AMS-1B crystalline molecular sieve-based catalyst compositions, and particularly, to the use of such compositions having improved para-selectivity for toluene methylation. More particularly, it relates to improved compositions comprising larger crystallite AMS-1B molecular sieves incorporated into an inorganic matrix which have been impregnated by a magnesium compound and to processes for using these improved compositions to selectively para-methylate toluene to xylene.
In U.S. Pat. Nos. 4,504,690, 4,128,592, and 4,086,287 is taught modifying a ZSM-5 aluminosilicate zeolite catalyst with P, Mg, or P/Mg oxides to obtain high proportions of the 1,4-dialkyl isomer. Phosphorus or Mg modified ZSM-5 zeolite catalysts for the disproportionation of toluene are shown in J. Appl. Polym. Sci. 36, 209 (1981). Disproportionation of toluene to produce benzene over P, Mg modified crystalline aluminosilicate zeolite catalysts is described in U.S. Pat. No. 4,137,195. Alkylation or disproportionation of certain monosubstituted benzene compounds to achieve nearly 100% selectivty to para-disubstituted derivatives over magnesium compound-modified ZSM-5 aluminosilicate zeolite catalysts is reported in J. Am. Chem. Sec. 101, 6783 (1979). In the same article an increase in para-selectivity is shown by larger crystal size ZSM-5 zeolite catalysts during toluene methylation.
Use of Mg alone or in combination with P to modify a ZSM-5 aluminosilicate zeolite catalyst is described in U.S. Pat. No. 4,049,573 and the modified catalyst is used for converting alcohols and ethers to hydrocarbons. Again, Mg is used to modify ZSM-5 zeolite catalysts in U.S. Pat. No. 4,002,698 which can be used for selective production of p-xylene from charge stocks of toluene and a C.sub.3 -C.sub.10 olefin; P modified catalysts for the methylation of toluene are also described.
Catalyst compositions, generally useful for hydrocarbon conversion, based upon AMS-1B crystalline borosilicate molecular sieve have been described in U.S. Pat. Nos. 4,268,420, 4,269,813, 4,285,919, and Published European application No. 68,796.
As described in the references in the paragraph above, catalyst compositions typically are formed by incorporating an AMS-1B crystalline borosilicate molecular sieve material into a matrix such as alumina, silica, or silica-alumina to produce a catalyst formulation. In one method of making AMS-1B crystalline borosilicate, sieve is formed by crystallizing sources for silicon oxide and boron oxide with sodium hydroxide and an organic compound. After crystallization, the resulting sodium form is ion exchanged with an ammonium compound and calcined to yield the hydrogen form of AMS-1B . In another and more preferred method, AMS-1B crystalline borosilicate is crystallized in the hydrogen form from a mixture containing a diamine in place of a metal hydroxide. AMS-1B borosilicates in hydrogen form are designated HAMS-1B . Typically, the hydrogen form sieve is gelled with an alumina sol, dried, and calcined to yield a catalyst composition.